Adjusting power of a control channel based on a characteristic of a message in the control channel

ABSTRACT

An entity, such as a base station, in a wireless communications network performs power control of a control channel based on one or more characteristics of a message in the control channel. For example, the control channel can be a paging channel. The one or more characteristics include, as examples, the size and/or the type of message in the control channel.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.13/957,607, filed Aug. 2, 2013, which is a continuation of U.S. Ser. No.13/539,594, filed Jul. 2, 2012, which is a continuation of U.S. patentapplication Ser. No. 10/389,473, filed Mar. 14, 2003, whose inventorsare Yuqiang Tang and Mark A. Harris, both which are hereby incorporatedby reference in their entirety as if fully and completely set forthherein.

TECHNICAL FIELD

This invention relates generally to adjusting the power of a controlchannel based on one or more characteristics of a control message to becommunicated over an air interface.

BACKGROUND

Mobile communications systems are made up of a plurality of cells. Eachcell provides a radio communication center in which a mobile stationestablishes a call with another mobile station or a wireline unitconnected to a public switched telephone network (PSTN) or a packet datanetwork. Each cell typically includes a radio base station, with eachbase station connected to a mobile switching center for processingcircuit-switched calls, or to a packet data serving node for processingpacket-switched communications.

Various wireless protocols exist for defining communications in awireless network. One such protocol is the time-division multiple access(TDMA) standard, According to TDMA, each radio frequency (RF) carriercarries a frame that is divided into plural time slots to increase thenumber of mobile stations that can be supported per RF carrier. Examplesof TDMA wireless networks include IS-136 and GSM (Global System forMobile) wireless networks.

Another type of wireless technology is provided by the code-divisionmultiple access (CDMA) standard. CDMA is a spread spectrum wirelesscommunications protocol in which transmission is based on the spreadspectrum modulation technique to allow many users to have access to thesame band of carriers.

Traditionally, wireless networks have been designed for carryingcircuit-switched voice traffic. However, with the explosion of theInternet and intranets, packet-switched communications (e.g., webbrowsing, electronic mail, and so forth) have become common. As aresult, third generation (3G) and beyond wireless technologies have beendeveloped to transition to higher bandwidth and more efficientpacket-switched communications over wireless networks.

One example of a 3G wireless technology is the CDMA 2000 technology, asdefined by the IS-2000 Standard. A CDMA 2000 wireless communicationssystem is capable of supporting both traditional voice traffic(circuit-switched voice traffic) as well as packet-switched traffic,such as web browsing, electronic mail, voice-over-IP (InternetProtocol), and so forth. Other types of 3G wireless technologies havealso been implemented, such as the 1×EV-DO, 1×EV-DV, UMTS (UniversalMobile Telecommunication System), and Enhanced GPRS (General PacketRadio Service) technologies, among others.

In conventional wireless systems, control and traffic channels aredefined for carrying control and traffic data, respectively. Toestablish a call, control signaling is initially exchanged between amobile station and a base station. For example, in a CDMA wirelessnetwork, a mobile station can originate a call by sending an originationmessage on an access channel to a base station. The base station in turnassigns various network resources to the mobile station by sending anassignment message to the mobile station over a paging channel. For amobile station-terminated call (in which the call is originated byanother endpoint and targeted to the mobile station), the base stationpages the mobile station on the paging channel.

Typically, certain control channels, such as the paging channel, arecommunicated at a fixed power level. The fixed power level of the pagingchannel is selected to achieve a compromise between reliability ofcommunication of control messages and available bandwidth or capacitywithin a given cell. The higher the power level of the paging channel,the lower the bandwidth or capacity available in a given cell. On theother hand, reducing the power level of a paging channel increases thelikelihood of errors occurring in the communication of control messagesbetween the base station and the mobile station, which reducesreliability of wireless communications.

Therefore, in conventional wireless communications networks, because thepaging channel is transmitted at a fixed power level, performance withina cell may not be optimized.

SUMMARY

In general, methods and apparatus are provided to dynamically adjust thepower level of a control channel for communicating control messages toenhance flexibility and performance. For example, a method of wirelesscommunications in a mobile communications network includes determiningat least one characteristic of a message to be communicated in a controlchannel, and adjusting a power level of the control channel based on thedetermined at least one characteristic of the message.

Other or alternative features will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless communications network.

FIG. 2 is a message flow diagram for establishing a call in the wirelesscommunications network of FIG. 1.

FIG. 3 is a flow diagram of a process of performing power control thatis part of establishing the call of FIG. 2.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details and that numerous variations ormodifications from the described embodiments may be possible.

Referring to FIG. 1, a wireless communications network 10 according toone example arrangement includes components that operate in accordancewith the CDMA (code-division multiple access) 2000 family of standards(collectively referred to as the IS-2000 Standard), which has beendeveloped by the Third Generation Partnership Project 2 (3GPP2).However, in other embodiments, other types of wireless protocols can beused for communications in the wireless communications network 10,including other versions of CDMA (e.g., IS-95, 1×EV-DO, 1×EV-DV), TDMAprotocols (e.g., IS-136, GSM), UMTS (Universal Mobile TelecommunicationSystem) protocols, Enhanced General Packet Radio Service (EGPRS)protocols, and so forth.

The wireless communications network 10 includes multiple cells 18 (onlyone shown in FIG. 1). The cell 18 includes a base transceiver subsystem(BTS) 20 for performing radio communications with mobile stations 16within the coverage area of the cell 18. The BTS 20 is connected to abase station controller (BSC) 22. Collectively, the BTS 20 and BSC 22are logically referred to as a “base station” 19, indicated by thebroken line in FIG. 1, with the understanding that multiple BTSs 20 can,and typically do, share one BSC 22. The role of the BSC is to manageresource allocation amongst the BTSs to which the BSC is connected. Suchresources include power control, channel management, and frequencymanagement, between a given BTS and mobile terminals in communicationwith the BTS. More generally, the terms “base station” and “accessnetwork” refer to any entity (or collection of entities) thatcommunicates wirelessly with mobile stations for communications sessions(e.g., circuit-switched call sessions, packet-switched voice callsessions, other packet-switched communications session, and so forth).

For communicating circuit-switched voice traffic, the BSC 22 is coupledto, and often is co-located with, a mobile switching center (MSC) 24,which is responsible for switching mobile station-originated orterminated traffic. Effectively, the MSC 24 is the interface for controlsignaling and user traffic between the wireless network 10 and otherswitched networks (such as a public switched telephone network (PSTN)26) or other MSCs.

The wireless communications network 10 according to the example alsosupports packet data services, in which packet data is communicatedbetween a mobile station 16 and another endpoint, which can be aterminal coupled to a packet data network 34 or another mobile stationthat is capable of communicating packet data. Examples of the packetdata network 34 include private networks (such as local area networks orwide area networks) and public networks (such as the Internet). Packetdata is communicated in a packet-switched communications sessionestablished between the mobile station 16 and another endpoint.

To communicate packet data, the BSC 22 is coupled to a packet controlfunction (PCF) module 32, which manages the relay of packets between theBSC 22 and a packet data serving node (PDSN) 30. The BSC 22 and PCFmodule 32 can be implemented on one platform or on multiple platforms.

In accordance with some embodiments, the base station 19 is able todynamically adjust the power level of a paging channel from the basestation 19 to a mobile station 16. Although reference is made to theadjustment of the power level of a paging channel, similar power controlcan also be performed for other control channels. To improve flexibilityand performance within a cell 18 (or cell sector), the power level ofthe paging channel is adjusted by the base station 19 based on one ormore characteristics of a control message in the paging channel, such asthe type and/or size of the control message.

As used here, adjusting the power level or power of a control channelrefers to adjusting the power of signaling (e.g., RF signaling) used tocarry the control channel. For example, the power of the signaling canbe increased by increasing the gain or amplification of the basebandsignal that carries the bit stream making up the information to betransmitted from the base station to the mobile station.

As the size of a control message increases, more frames are needed tocarry the control message. As the number of frames increases, thelikelihood of encountering error also increases. To counteract this, thepower level of the paging channel (or other control channel) can beincreased to reduce the error rate. Thus, in accordance with someembodiments, as the size of a control message in the paging channelincreases, the power level of the paging channel is also increased.

Since increasing the power level of the paging channel comes at theexpense of reduced bandwidth or capacity, it may not be desirable toadjust the power level of the paging channel for certain types ofmessages. For example, some messages are sent periodically by the basestation, such as system parameter messages. Because of the repeatedtransmission of these messages, errors in the reception of systemparameter messages are usually not fatal. On the other hand, if achannel assignment message (for assigning wireless network resourcesduring call setup) is not received successfully by a mobile station,then call establishment cannot proceed, which leads to callestablishment failure. Therefore, it is desirable to enhance thereliability of transmission of the channel assignment message in thepaging channel. The size of the channel assignment message can vary.

As further shown in FIG. 1, the BTS 20 includes a radio transceiver 50for communicating RF signaling between the base station 19 and themobile stations 16. The BTS 20 also includes a power control module 52that sets the power level of signaling communicated from the radiotransceiver 50 to the mobile stations 16.

According to one embodiment, the power level set by the power controlmodule 52 is controlled by a dynamic power management module 54 in theBSC 22. For each control message communicated over the paging channelfrom the base station 19 to a mobile station 16, the dynamic powermanagement module 54 determines what power level to set based on thetype of control message and/or the size of the control message. In analternative embodiment, the power control task performed by the dynamicpower management module 54 can be performed by the power control module52 in the BTS 20.

The BSC 22 also includes other modules, including a call processingmodule 56 that interacts with either the MSC 24 or the PDSN 30 forestablishing a call session. A “call session” refers to either acircuit-switched call session or a packet-switched communicationssession (for communicating real-time data such as voice data orconventional packet data such as web browsing data, electronic maildata, and so forth). Also included in the BSC 22 is a radio resourcesmanagement module 58 that controls assignment of radio resources for aparticular call that involves a mobile station 16 in the cell 18. Forexample, the radio resources assigned include traffic channels and otherradio resources.

Referring to FIG. 2, an example of a call flow is illustrated in whichpower control according to some embodiments is performed. FIG. 2illustrates a call that is originated by a mobile station. To originatea call, the mobile station transmits an origination message (at 102) tothe base station over an access channel to request service. The basestation acknowledges the receipt of the origination message with a basestation acknowledgement (BTS ACK) message (at 106) over the pagingchannel. However, prior to transmitting the BTS ACK message on thepaging channel, the base station first performs (at 104) power controlto set the power level of the paging channel.

Following transmission of the BTS ACK message on the paging channel, theMSC 24 interacts with the BSC 22 (and optionally the PDSN 30) todetermine whether service is to be provided to the requesting mobilestation, such as to determine whether traffic channels and otherresources are available to be allocated to the mobile station. Ifservice is to be provided, the base station transmits null traffic (at108) on the forward traffic channel to the mobile station. The basestation also prepares to communicate the allocated resources to themobile station via the channel assignment message (at 112) on the pagingchannel. Prior to sending the channel assignment message, the basestation performs (at 110) power control to set the power level of thepaging channel on which the channel assignment message is to becommunicated.

The channel assignment message defined by CDMA 2000 has an ASSIGN_MODEfield that can be set to one of several values. Each value ofASSIGN_MODE is associated with a specific combination of fields to beincluded in the channel assignment message. As a result, differentvalues of ASSIGN_MODE will cause the channel assignment message to varyin length. CDMA 2000 also defines an extended channel assignmentmessage, which has added fields and thus is generally larger in sizethan the basic channel assignment message. As used here, a “channelassignment message” refers to either the basic channel assignmentmessage or the extended channel assignment message. In other types ofnetworks, other types of control messages for assigning networkresources are communicated by a base station over control channels tomobile stations.

Once the forward traffic channel is established, the mobile stationsends (at 114) a traffic channel preamble (TCH Preamble) shortlyfollowed by null traffic data over the assigned reverse traffic channel.When the base station receives the TCH Preamble over the reverse trafficchannel, it sends the base station acknowledge (BTS ACK) message (at116) on the forward traffic channel back to the mobile station. Themobile station then acknowledges the reception of the BTS ACK message bysending an acknowledge (ACK) message (at 118) to the base station overthe reverse traffic channel.

At this point, the base station sends a service connect message (at 120)over the forward traffic channel to the mobile station to specify theservice configuration for the call session. The mobile station processestraffic in accordance with the specified service configuration. Onreceipt of the service connect message, the mobile station responds (at122) with a service connect completion message on the reverse trafficchannel. After further exchange of other control messaging, a callsession is established between the mobile station and base station inwhich data of voice traffic (or other traffic) can be communicated overthe traffic channels.

Also, periodically, the base station may send (at 126) control messagescontaining system parameters to mobile stations over the paging channel.Prior to sending the messages containing the system parameters, the basestation performs (at 124) power control to determine what power level toset the paging channel.

FIG. 3 shows an embodiment of performing power control (104, 110, 124)in accordance with an embodiment. The process of FIG. 3 can be performedby the dynamic power management module 54 (FIG. 1) in the BSC 22, oralternatively, the process can be performed by the power control module52 in the BTS 20. More, generally, the task shown in FIG. 3 is performedby a “module” that is located in the base station 19. The module firstdetermines (at 202) whether a message is to be transmitted over thepaging channel by the base station 19. If so, the module determines (at204) the type and size of the control message.

As discussed in connection with FIG. 2, examples of messages that can becommunicated over the paging channel include the BTS ACK message, achannel assignment message, general page message and a system parametersmessage. These are four different types of control messages that can becommunicated over the paging channel. Other control messages can also becommunicated over the paging channel. Also, certain control messages canvary in size (such as the channel assignment message) depending upon thefields that are inserted into these messages.

Based on the type and size of the control message, the module accesses(at 206) a lookup table 60 (FIG. 1) to determine what power level toassign the paging channel. The lookup table 60 essentially is a tablethat relates message types and sizes to power levels.

In the example message flow of FIG. 2, the channel assignment message isassigned a higher power level because of its size and its relativeimportance. The relatively large size of the channel assignment messagemeans that errors are more likely. An error in the channel assignmentmessage will usually cause call establishment to fail. On the otherhand, the BTS ACK message sent on the paging channel is typicallysmaller than the channel assignment, so that a lower power level (e.g.,default power level) can be assigned to transmit the BTS ACK messageover the paging channel. The system parameters message is sentperiodically over the paging channel. Thus, an error in one transmissionis usually not fatal, as the mobile station will receive another systemparameters message shortly. As a result, a system parameters message canalso be transmitted with the paging channel at a lower power level(e.g., a default power level).

The size of the channel assignment message can vary depending on thenumber of fields it is carrying. The module therefore also varies thepower level of the paging channel based on the variation in size of thechannel assignment message.

The power level for the size and type of the control message isretrieved from the lookup table 60 and the power level is set (at 208)by the module. Alternatively, instead of using the lookup table 60, themodule computes the power level using a predefined algorithm based onthe type and size of the message. If the module is located in the BSC22, the setting of the power level involves the BSC 22 communicating thepower level (in a parameter) to the BTS 20. However, if the module islocated in the BTS 20, then the power control module 52 sets the powerlevel by providing an indication to the radio transceiver 50.

By varying the power level of a control channel such as the pagingchannel depending on a characteristic (e.g., size and/or type), wirelesscommunications performance in a cell can be optimized. The moreimportant (and larger) control messages can be communicated with ahigher power setting for the control channel, whereas smaller or lessimportant control messages are communicated with a lower power settingfor the control channel. By varying the power level of a control channelsuch as the paging channel, an effective compromise between reliabilityand capacity can be achieved in a cell.

Instructions of the various software routines or modules discussedherein (such as the module for performing power control in the basestation) are stored on one or more storage devices in the correspondingsystems and loaded for execution on corresponding control units orprocessors. The control units or processors include microprocessors,microcontrollers, processor modules or subsystems (including one or moremicroprocessors or microcontrollers), or other control or computingdevices. As used here, a “controller” refers to hardware, software, or acombination thereof. A “controller” can refer to a single component orto plural components (whether software or hardware).

Data and instructions (of the various software routines or modules) arestored in respective storage units, which can be implemented as one ormore machine-readable storage media. The storage media include differentforms of memory including semiconductor memory devices such as dynamicor static random access memories (DRAMs or SRAMs), erasable andprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read-only memories (EEPROMs) and flash memories; magneticdisks such as fixed, floppy and removable disks; other magnetic mediaincluding tape; and optical media such as compact disks (CDs) or digitalvideo disks (DVDs).

The instructions of the software routines or modules are loaded ortransported to a system in one of many different ways. For example, codesegments including instructions stored on floppy disks, CD or DVD media,a hard disk, or transported through a network interface card, modem, orother interface device are loaded into the device or system and executedas corresponding software modules or layers. In the loading or transportprocess, data signals that are embodied in carrier waves (transmittedover telephone lines, network lines, wireless links, cables, and thelike) communicate the code segments, including instructions, to thedevice or system. Such carrier waves are in the form of electrical,optical, acoustical, electromagnetic, or other types of signals.

While the invention has been disclosed with respect to a limited numberof embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover such modifications and variations as fall within the truespirit and scope of the invention.

What is claimed is:
 1. A method for performing wireless communicationsin a mobile communications network, comprising: a communication devicedetermining a message to be communicated in a control channel; thecommunication device determining a power level for transmission of themessage using the control channel, wherein said determining the powerlevel comprises setting different power levels for different types ofmessages carried in the control channel, wherein a specific power levelis determined based on the message being an acknowledgement message, andwherein the power level for the acknowledgement message is a defaultpower level and wherein a power level for at least one other message ofa type different than the acknowledgement message is different than thedefault power level; the communication device setting the power levelfor transmission of the message based on said determining; and aftersetting the power level for transmission, the communication devicetransmitting the message in the control channel using the determinedpower level.
 2. The method of claim 1, wherein said determining thepower level is also based on the size of the message.
 3. The method ofclaim 2, wherein said determining the power level comprises using ahigher power level for larger messages and using a lower power level forsmaller messages.
 4. The method of claim 1, wherein said determining thepower level comprises using a higher power level for higher prioritymessages and using a lower power level for lower priority messages. 5.The method of claim 1, wherein the control channel comprises a pagingchannel.
 6. The method of claim 1, wherein the communication devicecomprises a base station.
 7. The method of claim 1, wherein the mobilecommunications network comprises one of an IS-95, CDMA (code-divisionmultiple access) 2000, 1×EV-DO, 1×EV-DV, UMTS (Universal MobileTelecommunication System), and EGPRS (Enhanced General Packet RadioService) system.
 8. A communication device for performing wirelesscommunicating, comprising: communication circuitry for performing thewireless communication; processing hardware coupled to the communicationcircuitry, wherein the controller is configured to operate with thecommunication circuitry to: determine a message to be communicated in acontrol channel; determine a power level for transmission of the messageusing the control channel, wherein said determining the power levelcomprises setting different power levels for different types of messagescarried in the control channel, wherein a specific power level isdetermined based on the message being an acknowledgement message, andwherein the power level for the acknowledgement message is a defaultpower level and wherein a power level for at least one other message ofa type different than the acknowledgement message is different than thedefault power level; set the power level for transmission of the messagebased on said determining; and after setting the power level fortransmission, transmit the message in the control channel using thedetermined power level.
 9. The communication device of claim 8, whereindetermining the power level is also based on the size of the message.10. The communication device of claim 9, wherein determining the powerlevel comprises using a higher power level for larger messages and usinga lower power level for smaller messages.
 11. The communication deviceof claim 8, wherein determining the power level comprises using a higherpower level for higher priority messages and using a lower power levelfor lower priority messages.
 12. The communication device of claim 8,wherein the control channel comprises a paging channel.
 13. Thecommunication device of claim 8, wherein the communication devicecomprises a base station.
 14. A non-transitory, computer accessiblememory medium storing program instructions for performing wirelesscommunications in a mobile communications network, wherein the programinstructions are executable by a processor of a communication device to:determine a message to be communicated in a control channel; determine apower level for transmission of the message using the control channel,wherein said determining the power level comprises setting differentpower levels for different types of messages carried in the controlchannel, wherein a specific power level is determined based on themessage being an acknowledgement message, and wherein the power levelfor the acknowledgement message is a default power level and wherein apower level for at least one other message of a type different than theacknowledgement message is different than the default power level; setthe power level for transmission of the message based on saiddetermining; and after setting the power level for transmission,transmit the message in the control channel using the determined powerlevel.
 15. The non-transitory, computer accessible memory medium ofclaim 14, wherein determining the power level is also based on the sizeof the message.
 16. The non-transitory, computer accessible memorymedium of claim 15, wherein determining the power level comprises usinga higher power level for larger messages and using a lower power levelfor smaller messages.
 17. The non-transitory, computer accessible memorymedium of claim 14, wherein the communication device comprises a basestation.